Problem: $ { {5} \times \left[\begin{array}{r}{4} \\ {2} \\ {0}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{r}{5}\times{4} \\ {5}\times{2} \\ {5}\times{0}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{20} \\ {10} \\ {0}\end{array}\right]}$